Additive sweetening of hydrocarbon oils with air, a phenylene-diamine and alcoholic alkali followed by a metal naphthenate



June 18, 1957 Filed May 4, 1955 United AStates Patent @dice Y 2,7916,3;84 Patented JuneA 1,8, 1957 ADDITIVE SWEETENING F HYDROCARBON UTLSWITH AIR, A PHENYLENE-DIAMINE AND ALCOHOLIC ALKALI FOLLOWED BY A METALNAPHTHENATE Johan C. D. Oosterhout, James L. Meadows, Gordon H.

Miller, and Frank L. Barger, Port Arthur, Tex., assignors to The TexasCompany, New York, N. Y., a corporation of Delaware Application May 4,1955, Serial No. 505,928

16 Claims. (Cl. 196-29) This invention relates to certain improvementsin the additive sweetening of hydrocarbon oils particularly lighthydrocarbon oils such as gasoline, naphtha and kerosene.

In the additive sweetening process certain materials are added to theoil streams in the run-down lines, extending from cracking, distillingor fractionating units to tankage, for the purpose of sweetening andstabilizing the hydrocarbon oil without the necessity of using specialtreating equipment for effecting these objects. The additives effect thesweetening and stabilizing of the hydrocarbon in the tank afferra periodof time.

An important object of the present invention is to effect a reduction inthe time required for the sweetening reaction so that the contents ofthe run-down tank can be quickly pumped to storage.

In accordance with the invention the hydrocarbon oil in the presence ofair is subjected to contacting with a phenylenediamine or a dialkylderivative thereof such as an N,N-dialkyl-para-phenylenediamine and withexpendable amounts of alcoholic alkali metal hydroxide, such aspotassium or sodium hydroxide, and certain organic salts, such as copperand cobalt naphthenates. By expendable amounts of caustic and copper orcobalt salts we refer to very minute quantities the recovery of whichmay be disregarded.

The additives are introduced into the oil stream flowing to a tank andsweetening is effected with a Very short time of standing in the tank.Frequently the oil in the tank will be found to be sweet as soon as itis full and generally the oil will be sweet within some two or threehours and in any case within about or 6 hours. After the oil is sweet ametal deactivator is added such as salicylalaminoalkane, preferably apolysalicylalpolyaminoalkane such as N,N'-disalicylal1,2-diaminopropane.On account of the presence of the salts of copper or cobalt it isdesirable to add a metal deactivator so that the treated oil will notonly be sweet and substantially free of mercaptans but will also bestabilized against oxidation and gum formation.

We find that a certain sequence in the addition of the additives must beadhered to in lorder to obtain rapid sweetening. Both copper naphthenateand cobalt naphthenate will react under certain conditions with sodiumhydroxide to form copper or cobalt hydroxides. The opportunity forreaction between the copper or cobalt naphthenate and the alkali metalhydroxide must be minimized. The most satisfactory method of preventingor reducing interaction between the caustic and copper or cobalt saltsis to add the copper or cobalt naphthenates last in the sequence of thesweetening additives. The order of addition of the other additives isnot of such critical nature; thus as to the phenylenediamine andalcoholic caustic either may be added first or they may be added at thesame point in the oil stream. The 4air may be introduced at anyconvenient'point in the stream. As stated after the sweetening reactionis completed the metal deactivator is added.

The alkali metal hydroxide is 'used in alcoholic solu- 2 tion. Theaqueous solution when used in expendable amounts in the combination ofadditives employeddoes not yield a sufficiently rapid rateofrsweetening. It appears that the presence of, the `alcohol may changethe mechanism of the sweetening reaction. Thus when usingy a solution ofsodium hydroxide Vin methyl alcohol it is possible that some sodiummethylate is formed which is sufficiently oil soluble or settles fromthe oil so slowly that increased contacting with the caustic is affordedwhich increases the rate of sweetening. The hydroxide may be used insolution with various alcohols such as ethyl, methyl and isopropyl.Methyl alcohol is the most satisfactory. The alcoholic hydroxide is usedin minute quantities not exceeding about 0.05 percent by volume of thehydrocarbon oil being treated. Proportions of the alcoholic causticvarying from about 0.002 to 0.05 percent have been found adequate tosupply the slight alkalinity desirable for sweetenngwith thecombinationof additives employed.

The copper naphthenate or cobalt naphthenate or mixtures thereof areadded to the oil in minute proportions of the order of about l to 10pounds of the naphthenate per 1000 barrels of oil being treated.

The air or` oxygen is added in a quantity at least approximating, andpreferably exceeding, the theoretical amount required for oxidizing themercaptans contained in the hydrocarbons. It appears that the presenceof the air is the most important factor in the combination influencingthe sweetening rate. i Y

As to the phenylenediamine oxidation inhibitor the preferred material isN,Ndisec.-butyl-para-phenylenediamine. This material is marketed undervarious trade names such as UOP No. 5, Du Pont No. 22 and Tenamene 2.The phenylenediamine is used in minute amounts such as about 5-10 lbs.per 1000 barrels of ol treated.

The combination of the additives mentioned effectually sweetens the oilat faster rates than havebeen possible in prior methods of additivesweetening. The time required for sweetening will not run over about 5to 6 hours and in some cases it is possible to have the tank sweet assoon as it is full. Furthermore, the invention makes it possible tosweeten stocks containing higher mercaptan sulfur contents than it hasbeen possible previously to sweeten by the additive technique. In viewof the addition of the copper or cobalt compounds to the oil it isdesirable at the completion of the treating described to add a metaldeactivator Such Vas a salicylalaminoalkane, preferably apolysalicylalpolyaminoalkane, such as N,N-disalicylal1,2-diaminopropane.About three parts of the metal deactivator to four parts of the coppernaphthenate will give a product of good`initial gum test and goodinduction period in the oxidation stability test. Y.' In typicaloperations in accordance with the invention `naphtha stocks weresweetened and stabilized by contacting with copper naphthenate within arange of about- 1 to 10 pounds per 1000 barrels of naphtha, with methylalcohol solutions of sodium hydroxide having-normalities approximating 4in quantities of 0.002 to 0.05 percent by volume of the naphtha or 1 to30 pounds NaOH per 1000 barrels, withN,N'-di-sec.-butyl-para-phenylenediamine in dosages varying from 7 to11.5 pounds per 1000 barrels and with air rates furnishing somewhatgreater For the purpose of more fully describing the'inventionA 3reference is had to the accompanying drawing or flow diagram showing apreferred embodiment of the invention.

The drawing shows a pipe manifold connected to a run-down tank 11. Theoil to be additive sweetened is directed through a line 12 to themanifold 10 from a cracking, distilling or fractionating unit or othersource. An oriiice 13 is provided in the manifold so as to eiTect anincrease in velocity and turbulence and improve the intimacy ofcontacting of the ingredients in the latter portion of the manifold justbefore the mixture enters the tank 11. The phenylenediamine inhibitor isadmitted to the manifold by a pipe 14 and the alcholic caustic entersthrough a line 15. Air is admitted by a line 16 and the copper or cobaltnaphthenate is introduced by a pipe 17. The sweetened produ-ct iswithdrawn through a line 18 into which the metal deactivator is injectedby a pipe 19.

In a series of runs made with the apparatus shown in the drawing themanifold 10 consisted of a 6 pipe 10' long.N,Ndi-sec.butylpara-phenylenediamine was admitted as a solution in lightnaphtha (48% phenylenediamine and 52% light naphtha). Copper naphthenatewas used in the form of an 8% copper liquid and was charged in solutionwith naphtha. The alcoholic caustic admitted was composed of anhydrousmethyl alcohol and dry flake caustic (76% NazO). The normality variedfrom 3.8 to 4.2. The charging stock was light naphtha from a fluidcatalyst cracking unit. It was taken directly from the distillateaccumulator on the unit and charged to the manifold pipe 10 and thenceto the run down tank 0 The accompanying table presents data obtained incertain of these runs. The table shows the average residence time inhours in the tank required for the naphtha to become sweet, the figuresincluding the actual time of standing after the tank was full plusone-half the time required to till the tank. The table shows thequantity of the phenylenediamine inhibitor in pounds per 1000 barrels ofnaphtha charge, the volume percent of caustic based on the naphthacharge, the type of caustic, the pounds of copper naphthenate perthousand barrels of naphtha charge, the air rate in pounds per hour andthe percentage of air based on the theoretical quantity of air requiredfor oxidizing the mercaptan sulfur content of the naphtha. In the lastcolumn the grams per liter of mercaptan sulfur based on the naphthacharge is given.

In another series of runs the additives were injected immediately intothe line from the distillate receiver on the fluid catalyst crackingunit and a slightly different sequence of addition was used. Thephenylenediamine inhibitor and alcoholic caustic were introduced intothe line together and then the air and copper naphthenate were injected.The run line from the distillate receiver to the run-down tank was some1500 feet long giving a time in the line of about four minutes and itwas found that this duration of time accompanied with the turbulent iiowin 'the pipe provided opportunity for considerable interaction betweenthe caustic and the copper naphthenate so that the effectiveness ofthese reactants in accomplishing sweetening was reduced. Improvedresults were obtained by injecting the copper naphthenate in the lineimmediately at the entrance to the run-down tank. The naphtha wassatisfactorily sweetened and stabilized by using more than thetheoretical quantity of air, with phenylenediamine in quantities ofabout 10 pounds per 1000 barrels of naphtha, with 0.002 volume percentalcoholic caustic and with copper naphthenate in amounts of about 3pounds per 1000 barrels and with the addition ofN,Ndisalicylal1,2-diaminopropane in amounts of about 2% pounds per 1000barrels.

A curious phenomenon in connection with the practice of the invention isthe apparent seeding effect of a sweet distillate in the bottom of thesettling tank is promoting the sweetening of the distillate admitted tothe tank. Thus when the distillate being treated is directe-d into atank which already contains sour tank bottoms, the time for sweeteningthe entire tank will be longer than if the tank contained some sweetdistillate in the rst place. Thus when the tank bottoms are sweet andmore than 100% of the theoretical amount of air required to oxidize themercaptans is used, the mer- `captan sulfur content of the distillate,being charged to the tank within reasonable limits, has no effect on thetime required for sweetening but if less than the theoretical amount ofair is used then the time required for sweetening increases with themercaptan sulfur content. Furthermore, we find that as long as the tankbottoms are sweet and more than 100% air is used, the copper naphthenatedosage, within reasonable limits, has no effect on the time required tosweeten but here again, even with sweet bottoms in the tank but withless than the theoretical amount of air, an increase in the quantityAverage Phenylene- Vol. Copper l Percent Run Residence diamine, PercentType Caustic Naphthe- Air Rate, Theoretical RSH-S e, lbs./M Causticnate, lbs/M lha/Hr. Air of Charge Hours bbls. bbls.

2. 5 9. 2 0. 022 alcoholic. 9. 6 13. 2 139 0. 034

19 11. 2 0.091 aqueous.. 6. 2 15.0 124 0. 053 18 9. 6 0.019 alcoholic.5.6 no air 0. 064

In these runs the orifice was used except in run E. Run G shows theeffect of using an expendable amount of aqueous caustic; at the end of19 hours the naphtha was still not sweet. Run H shows the effect of notintroducing air; in this case at the end of 18 hours the naphtha had notbecome sweet. N,Ndisalicylal1,2-diaminopropane was added to thesweetened naphtha in proportions of approximately three parts to fourparts of the copper naphthenate. The sweetened naphtha products hadsatisfactory copper dish and ASTM gum tests and the induction period bythe ASTM oxidation stability test was satisfactory. The gravity, Reidvapor pressure, and distillation were not altered significantly. An airinjection of even up to 0.035 pound of air per barrel of naphtha did notcause the loss of light ends.

of naphthenate decreases the time required for sweetening. We also iindthat when the tank bottoms are sweet the alcoholic caustic dosage,within reasonable limits, does y not affect the sweetening time as longas the theoretical cases tend to cause the vseparation of anaqueous-alcoholic phase which may be more or less'emulsied with somesweet naphtha in the bottom. It is felt that such alcoholic sodiumnaphthenate will act as a peptizer or dispersing agent for the freshincoming naphtha-copper naphthenatealcoholic caustic system and thatsuch a homogeneous system will react faster than a heterogeneous'systemand also will aiord greater solubility of the air or oxygen to speed upthe reaction.

Y In order to improve the contacting of the incoming charge oil with thesweetened naphtha in the bottom of the settling tank, naphtha from thelower part of tank 11 is recirculated to an upper portion of the tank orto the incoming line 10. For these purposes a pump 20 is provided whichdraws bottoms from the tank 11 and directs them either through line 21to an upper portion of the tank or through a line Z2 to the line 10preferably up stream from the orifice 13. The circulating sweetenednaphtha will contain a concentration of caustic and other constituentsthat promote the sweetening reaction and by contacting the oil beingsweetened with these components the rate of sweetening is increased.

Instead of employing the particular alcohols mentioned hereinbefore forthe alcoholic metal hydroxide solutions, acetylem'c alcohols, olefniclalcohols and glycols may be used, such for example as methylbutyonl,dimethyloctynediol, allylalcohol and ethylene glycol. The acetylenic andolefinic alcohols provide the unsaturation which is conducive to thesweetening reactions and consequently are well adapted for use in-thetreatment of straight run stocks.

Our investigations have shown that when admitting the oil into a lowerportion of the settling or run-down tank in the normal manner the oil atthe top of the tank will ordinarily have the highest-mercaptan sulfurcontent while the oil at the bottom of the tank will have the lowestcontent. This elect is believed to be due to the presence of greaterportions of the sweetening reagents in the lower sections of the tank.VConsequently an advantageous method of operation is to introduce themixture of o il and additives at the top of the tank or at the surfaceof the oil by means of a floating lswing line. By this procedure thesuspended caustic is required to pass through the total depth of the oiland While the tankV is being filled there will be suspended caustic atall levels. Additionally bottoms from tank vmay be withdrawn andcirculated through line 21 to an upper portion of the tank or throughline 22 to the incoming stream of oil and additives owing in line 10.

It has been found that the addition of cobalt naphthenatev to coppernaphthenate in the sweetening reaction produces surprising results. Theaddition of even small quantities of cobalt naphthenate to the coppernaphthenate produces a synergistic effect in increasing the rate ofsweetening. This synergistic effect is particularly noticeable in thetreatment of stocks which either have high contents of mercaptan sulfuror contain mercaptan sulfur compounds of particular refractoriness `andwhich in either case are diicult to sweeten. In a series of runs anaphtha stock containing 0.085 gram per liter of mencaptan sulfur wastreated. In each case the naphtha was contacted withN,Ndi-sec.-butyl-para-phenylenediamine in a quantity of 10 pounds per1000 barrels of naphtha, with alcoholic caustic amounting to 0.02 volumepercent of the naphtha and with either copper naphthenate `or cobaltnaphthenate or with certain mixtures of copper naphthenate and cobaltnaphthenate in each case using 5 lbs. of the naphthenate per 1000barrels of naphtha. The treatments were made in the presence of air.'I'he following table shows results obtained by treating with theseadditives, giving the mercaptan sulfur content in grams per literinitially, that is, immediately after the contacting and after variousperiods of standing. In run l copper naphthenate itself was used. In run2 cobalt naphthenate itself was used. In run 3 a mixture of 90% copper 6naphthenate and 10% cobalt naphthenate was used and in run 4 50% coppernaphthenate and 50% cobalt naphthenate.

Runl Run2 Run3 Run4 Ratio Copper Naphthenate to cobalt NaphthenateBSH-S, g./l.:

Initial After 12 hrs After 24 hrs-- After 60 hrs.

The use of mixtures of copper naphthenate and cobalt naphthenate incombination with the other additives thus presents an advantageousmethod of sweetening particularly as regards stocks that are diiiicultto sweeten.

Both straight run naphtha and thermally cracked naphtha generallysweeten more slowly by additive or inhibitor sweetening than lightcatalyst cracked naphtha. A particular advantage of the invention isconcerned with the additive sweetening of blends of straight run andthermally cracked naphtha. Thus the process of the invention involvingthe contacting with the phenylenediamine and with expendable amounts ofalcoholic caustic and copper naphthenate has been applied in theadditive sweetening of Various blends of straight run andthermallycracked naphtha. It was found that the addition of straight runnaphtha to thermally cracked naphtha makes it possible to quicklysweeten the straight run naphtha. As much as 40-50% of the crackedcomponent may be added to the straight run naphtha to obtain rapidsweetening and to produce a product of satisfactory gum test.

Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made Without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicatedin the appended claims.

We claim: Y

l. In the additive sweetening of light hydrocarbon oils containingmercaptans the process that comprises rst contacting the oil, in thepresence of air in an amount at least approximately as great as thetheoretical amount required to oxidize the mercaptans contained in theoil, with a phenylenediamine oxidation inhibitor and an alcoholic alkalimetal hydroxide solution in minute and expendable quantity, andsubsequently contacting said oil with a metal naphthenate selected fromthe group consisting of copper naphthenate and cobalt naphthenate inminute and expendable amount and permitting the oil to become sweet inthe presence of the additives.

2. In the additive sweetening of light hydrocarbon oils containingmercaptans wherein the oil is passed in a stream through a pipe to anenlarged settling zone the process that comprises introducing into afirst portion of the stream of oil a phenylenediamine oxidationinhibitor, an alcoholic alkali metal hydroxide solution in minute andexpendable quantity and air in an amount at least approximately as greatas the theoretical amount required to oxidize the mercaptans containedin the oil, introducing into a subsequent portion of the stream of oil ametal naphthenate selected from the group consisting of coppernaphthenate and cobalt naphthenate in minute and expendable amount andpermitting the oil to become sweet in the settling zone.

3. In the additive sweetening of light hydrocarbon oils containingmercaptans wherein the oil is passed in a stream through a pipe to anenlarged settling zone in the process that comprises introducing into afirst portion of the stream of oil a phenylenediamine oxidationinhibitor, an alcoholic alkali metal hydroxide solution in minute andexpendable quantity and air in an amount at least approximately as greatas the theoretical amount required` to oxidize the mercaptans containedin` the oil,

7 introducing into a subsequent portion of the stream of oil a metalnaphthenate selected from the group consisting of copper naphthenate andcobalt naphthenate in minute and expendable amount, permitting the oilto become sweet in the settling zone, and thereafter adding a metaldeactivator to the oil.

4. In the additive sweetening of light hydrocarbon oils containingmercaptans wherein the oil is passed in a stream through a -pipe to anenlarged settling zone the process that comprises introducing into a rstportion of the stream of oil a phenylenediamine oxidation inhibitor in aquantity of about to 10 pounds per 1000 barrels of oil, an alcoholicalkali metal hydroxide solution in a quantity of about 0.002-G.05% byvolume `of the oil and air in an amount at least approximately as greatas the theoretical amount required to oxidize the mercaptans containedin the oil, introducing into a subsequent portion of the stream a metalnaphthenate selected from the group consisting of copper naphthenate andcobalt naphthenate in a quantity of about l to pounds per 1000 barrelsof oil and permitting the oil to become sweet in the settling zone.

5. In the additive sweetening of light hydrocarbon oils containingmercaptans wherein the oil is passed in a stream through a pipe to anenlarged settling zone the process that comprises introducing into afirst portion of the stream of oil a phenylenediamine oxidationinhibitor in a quantity of about 5 to 10 pounds per 1000 barrels of oil,an alcoholic alkali solution of sodium hydroxide in a quantity amountingto about 1-30 pounds NaOH per 1000 barrels of oil and air in an amountat least approximately as great as the theoretical amount required tooxidize the mercaptans contained in the oil, introducing into asubsequent portion of the stream a metal naphthenate selected from thegroup consisting of copper naphthenate and cobalt naphthenate in aquantity of about 1-10 pounds per 1000 barrels of oil and permitting theoil to become sweet in the settling zone.

6. In the additive sweetening of light hydrocarbon oils containingmercaptans wherein the oil is passed in a stream through a pipe to anenlarged settling zone the process that comprises introducing into afirst portion of the stream of oilN,N'-di-sec.-butyl-para-phenylenediamine, an alcoholic alkali metalhydroxide solution in a quantity of about 0.002-0.05% by volume of theoil and air in an amount at least approximately as great as thetheoretical amount required to oxidize the mercaptans contained in theoil, introducing into a subsequent portion of the stream of oil coppernaphthenate in an amount of about 1-10 pounds per 1000 barrels of oiland permitting the oil to become sweet in the settling zone.

7. In the additive sweetening of light hydrocarbon oils containingmercaptans wherein the oil is passed in a stream through a pipe to anenlarged settling zone the process that comprises introducing into afirst portion of the stream of oil N,N-di-sec.-butyl-parapheny1enediamine, an alcoholic solution of sodium hydroxide in a quantityamounting to about l-30 pounds NaOH per 1000 barrels of oil and air inan amount in excess of the theoretical amount required to oxidize themercaptans contained in the oil, introducing into a subsequent portionof the stream of oil copper naphthenate in an amount of about l-10pounds per 1000 barrels of oil, permitting the oil to become sweet inthe settling zone and thereafter adding salicylalaminoalkane to the oil.

8. The process as deiined in claim 7 wherein the salicylalaminoalkaneadded to the oil is N,N-disalicylall,2 diaminopropane.

9, In the additive sweetening of light hydrocarbon oils containingmercaptans the process that comprises contacting the oil in the presenceof air with a phenylenediamine oxidation inhibitor, an alcoholic alkalimetal hydroxide solution in minute and expendable quantity and metalnaphthenate in minute and expendable amount and consisting essentiallyof copper naphthenate and cobalt 8 naphthenate and permitting the oil tobecome sweet in the presence of the additives.

' 150."The process as defined in claim 9 wherein the cobalt naphthenateconstitutes atleast about 10% of said metal naphthenate.

11. In the additive sweetening of light hydrocarbon oils containingmercaptans wherein the oil is passed in a stream through a pipe to asettling tank, the process p that comprises introducing into the streamof oii a phenylenediamine oxidation inhibitor, an alcoholic alkali metalhydroxide solution in minute and expendable quantity, a metalnaphthenate selected from the group consisting of copper naphthenate andcobalt naphthenate in minute and expendable amount and air in an amountat least approximately as great as the theoretical amount required tooxidize the mercaptans contained in the oil and contacting the oil beingsweetenedA with previously sweetened oil containing constituents whichpromote the sweetening reaction.

12. In the additive sweetening of light hydrocarbon oils containingmercaptans wherein the oil is passed in a stream through a pipe to asettling tank, the process that comprises introducing into the stream ofoil a phenylenediamine oxidation inhibitor, an alcoholic alkali metalhydroxide solution in minute and expendable quantity, a metalnaphthenate selected from the group consisting of copper naphthenate andcobalt naphthenate in minute and expendable amount and air in an amountat least approximately as great as the theoretical amount required tooxidize the mercaptans contained in the oil, withdrawing sweetened oilfrom the bottom of the tank containing constituents which promote thesweetening reaction and circulating the withdrawn oil to an upperportion of the tank.

13. In the additive sweetening of light hydrocarbon oils containingmercaptans wherein the oil is passed in a stream through a pipe to asettling tank, Ithe process that comprises introducing into Vthe streamof oil a phenylenediamine oxidation inhibitor, an alcoholic alkali metalhydroxide solution in minute and expendable quantity, a metalnaphthenate selected from the group consisting of copper naphthenate andcobalt naphthenate in minute and expendable amount and air in an amountat least approximately as great as the theoretical amount required tooxidize the mercaptans contained in the oil, withdrawing sweetened oilfrom the bottom of the tank containing constituents which promote thesweetening reaction and injecting the withdrawn oil to the stream of oiland additives owing to the tank.

14. In the additive sweetening of light hydrocarbon oils containingmercaptans wherein the oil is passed in a stream through a pipe to aysettling tank, the process that comprises introducing into the stream ofoil a phenylenediamine oxidation inhibitor, an alcoholic alkali metalhydroxide solution in minute and expendable quantity, a metalnaphthenate selected from the group consisting of copper naphthenate andcobalt naphthenate in minute and expendable amount and `air in an amountat least approximately as great as the theoretical amount required tooxidize the mercaptans contained in the oil, permitting the oil tobecome sweet in the settling tank, withdrawing from the bottom of the-tank settled alkaline components comprising alkalli metal hydroxide,phenolate and naphthenate and recycling such settled components intoContact with the oil being sweetened.

15. In the additive sweetening of a light hydrocarbon oil containingmercaptans wherein the oil is passed in a stream through a pipe to anenlarged settling zone, the process that comprises introducing into afirst portion of the stream of oil a phenylene-diamine oxidationinhibitor, an alcoholic alkali metal hydroxide solution and air in anamount at least approximately as great as the theoretical amountrequired to oxidize the mercaptans contained in the oil, and introducinginto a subsequent portion of the stream of oil, copper naphthenate andcobalt naphthenate.

16. In the additive sweetening of a light hydrocarbon oil containingmercaptans wherein'the oil is passed in a stream through a pipe to asettling tank, the process that comprises introducing into the stream ofoila phenylene-diamine oxidation inhibitor, an alcoholic alkali'- asgreat as the ytheoretical amount required to oxidizethe mercaptanscontained in the oil, withdrawing `sweetned oil from the bottom of thetank containing constituents which promote the sweetening reaction andcir- Rosenwald Nov. 4, 1952 Krause et a1. Dec. 22, 1953

1. IN THE ADDITIVE SWEETENING OF LIGHT HYDROCARBON OILS CONTAININGMERCAPTANS THE PROCESS THAT COMPRISES FIRST CONTACTING THE OIL, IN THEPRESENCE OF AIR IN AN AMOUNT AT LEAST APPROXIMATELY AS GREAT AS THETHEORETICAL AMOUNT REQUIRED TO OXIDIZE THE MERCAPTANS CONTAINED IN THEOIL, WITH A PHENYLENEDIAMINE OXIDATION INHIBITOR AND AN ALCOHOLIC ALKALIMETAL HYDROXIDE SOLUTION IN MINUTE AND EXPENDABLE QUANTITY, ANDSUBSEQUENTLY CONTACTING SAID OIL WITH A METAL NAPHTHENATE SELECTED FROMTHE GROUP CONSISTING OF COPPER NAPHTHENATE AND COBALT NAPHTHENATE INMINUTE AND EXPENDABLE AMOUNT AND PERMITTING THE OIL TO BECOME SWEET INTHE PRESENCE OF THE ADDITIVES.